Electrical protective device



R. M. SPUR-CK. ELECTRICAL PROTECTIVE DEVICE. APPLICATION FILED 0CT.10, 1917.

Patented Feb. 7, 1922.

Rebel" UNITED STATES PATENT OFFICE.

ROBERT M. SIURCK, OF SCHENECTADY, NEW YORK, ASSIGNOR- TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRICAL PROTECTIVE DEVICE.

Specification of Letters Patent.

Patented. Feb. '7, 1922.

Application filed October 10, 1917. Serial No. 195,838. 7

To all whom it may concern:

Be it known that I, ROBERT M. SPUROK, a citizen of the United States, residin at Schenectady, county of Schenectady, tate of New York, have invented certain new and useful Improvements in Electrical Protective Devices, of which the following is a specification.

My invention relates to electrical protective devices, particularly to relays, and has for its object to provide a relay of the retarded or time limit type which is reliable and certain in its action, and which has time current characteristics controllable to give the relay a wide range of selectivity in its operation.

Relays responsive to conditions of overload and operative with a time delay when connected in an electrical system of distribution operate satisfactorily on normal conditions of overload but upon abnormal or excessive conditions, such devices often operate regardless of their time limit setting. This effect is particularly disadvantageous when a plurality of relay devices respond to the same abnormal conditions and are desired to operate in a definite and certain sequence. In such instances, a very heavy overload due, for instance, to a short circuit, will cause all the relays to operate simultaneously or in the wrong sequence. This action is due to the fact that the time current characteristics of the relays are such that for wide variations in current, especially at the knee of the time current curve corresponding to high current values, there are only very slight variations in time delay, thus impairing the selective action of the relay.

According to my invention, I provide a relay embodying means for modifying the time current characteristics of the relay and controlling its time current curve in such a manner as to provide a greatly improved selective action, especially upon excessive currents. I accomplish the purposes of my invention by providing a relay embodying a reactive means having a magnetic circuit adapted to be saturated on currents above a predetermined amount and means for controlling the saturation point of the circuit and the impedance of the reactive means.

The novel features which I believe to be characteristic of my invention will be definitely indicated in the claims appended hereto, while the features of construction and mode of operation will be understood by reference to the following description taken in connection with the accompanying drawings in which Fig. 1 shows diagrammatically a relay of the time limit type embodying the features of my invention, and Figs. 2 and 3 show diagrammatically time limit relays embodying my invention in modified form.

In Fig. 1, I have shown a relay of the time limit, type, and by way of illustration, a plunger type of relay, comprising a magnetic core member 1 controlled by an actuating winding 2. The plunger or core 1 carries the usual bridging or movable contact member 3 cooperating with fixed contacts 4 to control an auxiliary circuit, which may be the circuit of a trip coil for an oil circuit breaker or any other control circuit. The relay winding 2 is connected in the secondary circuit of a transformer, 5, which is responsive to current conditions in a-conductor 6. The plunger or movable member 1 is provided with a time delay means, for instance, a dash pot 7 operating to retard the movable member 1 or to introduce a timeinterval between the energization of the actuating winding 2 and the engagement of the contacts 3 and 4:.

The time limit relay is provided with a control or reactance device 8 for modifying the characteristics of the relay comprising a reactive or inductive winding 9 connected in shunt to the actuating winding 2 for the relay and provided with a magnetic circuit adapted to saturate before the magnetic circuit of therelay. Due to the impedance of the reactance shunt and its reactive effect,

little current will flow through it, the greater proportion of the secondary current from transformer 5 passing through the actuating winding 2 for the relay up to a predetermined value of current which is determined by the saturation of the magnetic circuit of the reactance shunt. Above this predetermined value of secondary current, the reactanoe shunt acts as a saturated reactance, the voltage drop cross the reactance being substantially constant, thus limiting the voltage drop across the actuating winding 2 to substantially a constant value. The reactance shunt thereby takes a greater proportion of the secondary current so that above the predetermined value of secondary current which causes the reaotance shunt to saturate, the amount of such current taken by the actuating winding 2 is substantially constant. In the relay ofmy invention, I

have provided a means for controlling or modifying the saturation of the reactance shunt in such a manner that the predetermined value of current required to saturate vided for the circuit including legs 11 and" the reactance shunt can be varied at Will.-

For obtaining this function, I provide the inductive winding 9 with a magnetic member 10 having three legs 11, 12 and 13, the winding 9 being wound on one leg 11 and having a magnetic circuit which includes legs 11 and 12. The leg 12 is made of smaller cross-section than the remainder of the circuit to provide saturation characteristics. A

magnetic shunt, including leg 13, is pro-.

12, the effect of which or the reluctance of which \can be varied by an air gap 14 adjustable by a wedge member 15. The predetermined value of secondary current required'to saturate leg 12 can be modified and controlled by the adjustable air gap 14 by shunting more or less of the flux through leg 13 and hence the time current chractering a force opposing the force of the actu-.

ating winding 2 which is a measure of the flux flowing through the magnetic shunt or the circuit including leg 13. For this purpose I provide a winding 16 on the magnetic member 10 between the legs 12 and 13 which serves to transmit current to a winding 17 acting on the plunger 1 and wound to oppose the action of the actuating winding 2 o the movement ofthe plunger-to contact closing position. The amount of cur-, rent passing through winding 16 ,and hence the amount of restraining action or counter pull exerted by winding 17 is varied as the air gap 14 is varied and is a measure of the reluctance of the shunt including the leg 13..

On overloads below a predetermined amount which is determined by the air gap 14, the impedance of the relay and reactive means 8 are substantially constant. Thus the operating characteristics of the relay are substantially independent of the reactive means 8 on overloads. below the predetermined amount; On overloads over this predetermined amount, the flux set up by the winding 9 divides between the circults including legs 12 and 13 depending on the setting of air gap 14, thus regulating the impedance of the reactance device and producing a modifying effect on the actuating winding not only by the reactance device per se but bythe flux traversing the leg 13 and exerting a force through winding 17 opposing the actuation of the relay.

' Whereas in Fig. 1 a non-automatic'means is shown for modifying the action of the relay or. controlling the saturation of the reactance device, in Fig. 2 the impedance of the reactive device or the force opposing the relay is varied automatically. In this modification, the reactive device 8 having the reactive winding 9 is provided with'a magnetic member 18 having a single magnetic circuit which is adapted tobe auto- .matieally controlled by a wedge shaped member-19 carried by the plunger or movable member 1 of the relay. Depending on the character of the time current characteristics required, the plunger of the relay in operating may move the wedge member 19 to open or close the circuit of member 18. In Fig. 2 the wedge 19 is shown as being normally in closed position and opened as the relay operates. tions, therefore, the impedance of the reactance means 8 is large causing the relay winding 2 to take-a greater proportion of the current from. the secondary of transformer 5. Upon heavy overloads, however, the movement of the relay plunger 1 to circuit closing position moves the wedge-member 19 to open the magnetic circuit of member 18 to provide an air gap and as the relay operates, the gap is proportionally increased thereby reducing the impedance of the reactive device 8 and causingit to take an increasing amount of the overload current, thus robbing the relay winding 1 and modifying the characteristics of the relay as already described.

In Fig, '3, another modification of my invention is shown, in which the reactance device 8 comprises a movable plunger 20 actuated by a winding 21. When the plunger 20 is in its lower position, the reactance of Under normal condi- V the winding 21 is a minimum and the winding 2 of the relay is shunted by a low impedance. Upon a predetermined current,the plun n20 israised and the reactance of the win ing 21 increased thereby shunting less current from the winding 2 and causing the relay plunger'l to be raised If this predetermined overload exists for 'a predetermined length of time, the relay plunger 1 .will be operated to close the contacts of the relay. IVith greater overloads, the magnetic member 22 will approach more and more nearly to saturation thereby shunting more and more' ,current from the winding 2, t us modifying the characteristics of the relay as already described in connection with the modifications of my invention shown in Figs. land 2.

In accordance with the provisions of the patent statutes, I have described the" principle of operation of my invention, together the apparatus which I now consider to represent the best embodiment thereof; but

I desire to have it understood that the apparatus shown is only illustrative, and that the invention can be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is:-

1.- A protective device comprising an actuating winding, a movable retarded circuit controlling member controlled by said winding, reactive means in shunt to said winding having a magnetic circuit adapted to saturate on currents above=a predetermined amount to modify the action of said winding and means for controlling the point of saturation of said magnetic circuit.

2. A protective device comprising an actuating winding, a movable retarded circuit controlling member controlled by said winding, and means for modifying the time current characteristics of said device on currents above a redetermined amount including an inductive winding in shunt to said actuating winding, a magnetic circuit for said inductive winding having a portion adapted to saturate on currents above a predetermined amount, and means for regulating the flux through said portion to control the saturation'of said magnetic circuit.

3. A protective device comprising an actuating winding, a movable ret'arded circuit controlling member controlled by said winding, an inductive winding inshunt to said actuating winding, a magnetic circuit for said inductive windin adapted to saturate on excess currents aving a portion thereof including an air gap, and means for varying said air gap to control the saturation of said magnetic circuit.

4. In a time limit relay, a movable retarded circuit controlling member, an actuating winding therefor, an inductive device inshunt to said actuating winding, a magnetic member operatively related to said inductive device,;and means exerting a force on said current controlling member op osing the force of said actuating win 'n which is'a measure of the reluctance of sai inductive device.

5. In a time limit relay, a movable retarded circuit controlling member, an actuating' winding therefor, an inductive winding in shunt to said' actuatingwinding, a

vmagnetic member operatively related to said inductive winding adapted to saturate on a current above a predetermined value, and means whereby the predetermined value of current required to produce saturation can be regulated.

6. A protective device comprising an actuating winding, a movable retarded circuit controlling member controlled by said winding, an inductive winding in shunt to said actuating winding, a magnetic circuit for said inductive winding adapted to saturate on currents above a redetermined amount, and means controlled by said current controlling member for varying the reluctance of said magnetic circuit.

In witness whereof, I have hereunto set my hand this 9th da of October 1917.

RohER'r M. srURoK. 

